Fuel control with feedback and force multiplication



Sept. 12, 1961 F. c. REGGIO 2,999,488

FUEL CONTROL WITH FEEDBACK AND FORCE MULTIPLICATION Original Filed Feb.5, 19:59

United States The present application is a division of my applicationSerial No. 591,511 filed June 7, 1956, which is a continuation of SerialNo. 496,296 filed July 27, 1943, now abandoned, which in turn is adivision of Serial No. 254,355 filed February 3, 1939, now alsoabandoned.

The invention relates to fuel control devices for combustion engines,and more particularly to devices for automatically controlling theengine supply of liquid fuel, or the relative proportions of the fueland air composing the engine combustible mixture.

An object of the invention is to provide improved devices of the typeindicated utilizing feedback and force multiplication.

Further objects of the invention will be apparent from the followingdescription, taken in connection with the appended drawing which is adiagrammatic sectional View of a device embodying the invention.

The invention is in no way limited to use with reciprocating engines,but may be practiced in connection with any suitable thermal orcombustion engine.

Referring more specifically to the drawing, the arrangement showntherein comprises an engine 60 having an induction passage 59communicating with the inlet side of a supercharger or compressor 61 ofany suitable type, which in turn leads to an induction pipe 62 andthence to the inlet port, not shown, of the engine. The passage 59 iscontrolled by a throttle valved? actuated through a lever 64.

A casing 80, communicating through a large duct 81 with the inductionpipe 62, contains air at induction pressure and temperature. Anevacuated bellows 82 in said casing acts on lever 83 to operate rod 94and pilot valve 84, 85 which controls admission of oil under pressure,usually led from the engine lubricating system through pipes 87 and 8%as indicated by thejarrows, to opposite sides of piston as. Low pressureoil is returned to the engine sump through line 89. A floating lever 90is connected at its ends with rod 94 and piston 86, and at anintermediate point with rod 91 which is connected, through lever 92 androd 93, with the horizontal arm of a bell-crank lever 74.

Also enclosed within casing 80 there is a bellows 95 which containing adefinite weight of gas or other suitable iluid at constant volume. Thehigh velocity of the air flow in the induction manifold 62 as well asthe pulsations of pressure therein determine eddy currents andturbulence within the large and short conduit 81 and casing 80, thuscausing an active thermic exchange, by conduction and convection,between the air flowing in the manifold 62 and the bellows 95.Furthermore the thermal capacity of the latter is extremely small, andit follows that the fluid within bellows 95 is at all times maintainedat the same temperature as the air in the pipe 62.

The absolute pressure within bellows 95 is therefore proportional to theabsolute manifold or induction temperature. Bellows 95 and a similar andevacuated bellows 96 act against each other and on a lever 97 to operaterod 100 of a servo mechanism similar to the servo motor 86. Enginelubricating oil is led thereto and atent Patented Sept. 12, 1961evacuated therefrom as indicated by the arrows. The pressure of the airin casing acts in opposite directions on bellows and 96, therebybalancing out the eifect of any pressure change therein, so that theload transmitted to lever 97 by the two bellows is only dependent on theinduction or manifold temperature. The servo mechanism controlled by rodacts on lever 98 to vary the operating distance of rod 93 from thefulcrum. of lever 92. Spring 99 balances the load transmitted by thebellows to rod 100 and is designed so that the operating distance of rod93 from the fulcrum of lever 92 is proportional to the actual absolutemanifold temperature. Any temperature change in the induction manifoldoperates bellows 95 and in turn the servo mechanism to rotate lever 98and vary the load of spring 99 until the balance of the rod 100 in itsneutral position is restored. Thus the load on rod 93 is proportional tothe absolute pressure and inversely proportional to the absolutetemperature in the induction pipe 62, and therefore is directlyproportional to the air density therein.

A control lever 78 is adapted to modify the angular setting of lever 79and in turn to alter the distance of the lower end of rod 93 from thefulcrum of lever 74.

The engine 60 is provided with a fuel feed, such for example as aconventional injection or metering pump 104 driven by the engine andcomprising one or more pump elements connected. by ducts or pipes andnozzles 70 with the various engine cylinders. These nozzles 79 may bemounted in any suitable position, such as near the intake cylinder portor valve or inside the cylinder, or they may be mounted to inject fuelinto the induction pipe 62, as shown in detail in the parentapplication.

The delivery of the engine fuel feed or metering pump is adjusted byaxially displacing the control rod 106. This rod is biased by a spring107 and is actuated by the upper arm of the bellcrank lever 74. Thespring 107 is so designed as to exert on the control rod 106 a loadwhich is proportional to the quantity of fuel delivered per cycle by themetering pump 104.

The device works as follows: the evacuated resilient bellows 82 exertson the rod 94 an upward load. or force proportional to the inductionpressure. in normal operation the rod 94 with the control valves 84 and85 is maintained in equilibrium in neutral position by a down ward loadof equal magnitude transmitted thereto from the calibrated spring 107 ofthe fuel metering pump 104. Thus, for a given adjustment of thetemperature compensating lever 98 and manual control lever 78 theinduction pressure and the load of the spring 107 (and in turn theengine fuel supply) are proportional. If now the pilot operates theengine throttle control lever 65 in a direction to decrease the engineair supply, or if the aircraft climbs to higher altitude, the inductionpressure surrounding bellows 82 decreases, and with it decreases theupward load transmitted by the bellows to the rod 94, while the downwardload transmitted thereto from the spring 107 remains unchanged.

Thus the bellows 82 expands, the rod 94 moves downward, and oil underpressure admitted over piston 86 displaces the same downward, causingcounter-clockwise rotation of lever '74 and movement of the control rod106 to the left, thereby decreasing the engine fuel supply. As thespring 107 expands, its load decreases and determines a correspondingdecrease of the downward load applied to the rod 94. As a result thedownward motion of the latter is stopped, and thereafter the rod 94moves upward toward its neutral position. The downward movement of thepiston 86 continues until the loads transmitted to the rod 94 by thespring 107 and by the induction pressure have once more equal magnitudesand rod 94 resumes its neutral position. Obviously, an increase ofinduction pressure, due either to a change of adjustment of the throttlecontrol lever 65 or to a decrease of altitude, causes a correspondingincrease of the engine fuel supply. Induction pressure and fuel deliveryper cycle thus vary proportionally.

As already stated, lever 97 actuated by bellows 95 and 96 exerts on rod100 an upward load which is proportional to the induction temperature.In normal operation, that is to say when said temperaure is constant,said. load is balanced by the spring 99, and the rod 100 is in itsneutral position. An increase in induction temperature causes aproportional increase of pressure within bellows 95 and upward loadapplied to the rod 100. Bellows 95 expands, the rod 100 is lifted, andoil under pressure is led above the piston of the servomotor, thuscausing lever 98 to rotate counter-clockwise, and gradually increasingthe load ofspring 99. This increase in the spring load causes the rod100 to move downward toward its neutral position. Operation of theservomotor and rotation of lever 98 continue until rod 160 resumes itsneutral position, the load of spring 99 having in the meantime assumed avalue equal to the new upward load exerted on the rod 190 by the bellowsand corresponding to the new value of the induction temperature; theresult being that lever 93 assumes a new position of equilibrium inwhich the distance of rod 3 from the fulcrum of lever 92 has increasedin proportion to the increase of absolute induction temperature.

Thus the load exerted by the rod 93 to the bell-crank lever 74 isproportional to the absolute pressure and inversely proportional to theabsolute temperature in the induction pipe 62, and is thereforeproportional to th air density therein.

The mixture control lever 78 is adapted to modify the distance of rod 93from the fulcrum of lever 74 so as to vary the proportionality ratiobetween the air density in theinduction pipe 62 and the fuel deliveryper cycle.

If the air charge per cycle, or weight of air present in the enginecylinder during the compression and power strokes, is proportional tothe induction density, then the mechanism shown in the drawing gives foreach adjustment of the mixture control lever 78 a corresponding constantfuel-air ratio.

In certain engines it has been found that the air charge is inverselyproportional not to the absolute induction temperature, but to thesquare root thereof, or a still different function of said temperature;and it has further been observed that the said air charge may beaffected by the surrounding pressure. In this connection variouscompensating devices are disclosed in the parent cases.

It is to be clearly understood that while the fuel metering pump 104described above and illustrated in the drawing is a conventionalmulti-plunger variable-delivery fuel injection pump, and means forautomatically controlling the fuel delivery or the fuel-air ratioaccording to the present invention may be applied to any suitable fuelsupply system.

, The arrangement described above, in which the engine fuel flow or thefuel-air ratio can be adjusted only man ually by the pilot or operatorthrough the control lever 78 is not the most suitable in connection withaircraft engines. Accordingly, means responsive to one or more engineoperative conditions, such for example as the induction manifoldpressure or density, engine speed, atmospheric pressure, enginetemperature may be provided for controlling said fuel supply or fuel-airratio automatically, as described in detail in the parent cases.

1 Where the claims are directed to less than all of the elements of thecomplete system disclosed, they are inservo motor control valve, a valveactuating mechanism, pressure responsive means connected with said airintake system downstreamfrom the compressor for transmitting to the saidvalve actuatingmechanism a first force substantially proportional to thecompressor discharge pressure in the direction to increase the rate ofengine fuel supply, and a feed-back spring connected with the fuelcontrol member and adjusted thereby for applying to the same valveactuating mechanism a second force opposing said first force and varyingin predetermined relation to the position of the fuel control member,the arrangement being such that during steady operation the saidactuating mechanism is in equilibrium under said two forces actingagainst each other, but as soon as such equilibrium is disturbed thesaid actuating mechanism will move the servo motor control valve and setin motion the servo motor to vary the adjustment of the fuel controlmember and thereby alter the said second force set up by the feed-backspring until the equilibrium of the valve actuating mechanism isrestored.

2. In a fuel control for an engine having an air intake system with acompressor therein, a fuel control member controlling the rate of fuelsupply to the engine, a servo motor for positioning said control member,a servo motor control valve, a valve actuating mechanism, compressordischarge pressure responsive means connected tothe valve actuatingmechanism for transmitting thereto a first force tending to increase therate of engine fuel supply, and a feed-back spring connected with thefuel control member for transmitting to the valve actuating mechanism asecond force opposing said first force and varying substantially indirect proportion to the rate of engine fuel supply.

3. In a fuel control for an aircraft engine having an air intake systemwith a compressor therein, a fuel control member for controlling therate of fuel supply to the engine, a hydraulic servo motor forpositioning said control member, a servo motor control valve, a valveactuating mechanism, compressor discharge pressure responsive meansconnected to the valve actuating mechanism for transmitting thereto afirst force indicative of the rate of engine air flow and tending tomove the fuel con-' trol member in the direction to increase the rate ofengine fuel supply, and a feed-back spring connected with the fuelcontrol member for transmitting to the valve actuating mechanism asecond force for opposing and balancing the said first force andindicative of the rate of engine fuel supply to maintain the desiredfuel-air ratio irrespective of changes in altitude. v

4-. In a fuel control for an aircraft engine having an air intake systemwith a compressor therein, a fuel control member controlling the rate offuel supply to the engine, a servo motor for positioning said controlmember, a servo motor control valve, a valve actuating mechanism,compressor discharge pressure responsive means connected to the valveactuating mechanism for transmitting thereto a first signal tending toincrease the rate of engine fuel supply, a feed-back spring connectedwith the fuel control member for transmitting to the valve actuatingmechanism a second signal opposed to the first signal and indicative ofthe rate of engine fuel supply to maintain the desired fuel-air ratioirrespective of changes in altitude, and a variable-ratio device in saidvalve actuating mechanism for changing the magnitude of one of said twosignals to vary the engine fuel-air mixture ratio.

5. In a fuel control for an engine having an air intake system with acompressor therein, a fuel control member for controlling the rate offuel supply to the engine, a servo motor for positioning said controlmember, a control element for controlling the servo motor, an actuatingmechanism for said control element, compressor discharge pressureresponsive means'for transmitting to said actuating mechanism a firstsignal in the direction to increase the engine fuel-supply, a feed-backspring connected with said fuel control member for transmitting to saidactuating mechanism a second signal opposed to the first signal andvarying substantially in proportion to the engine fuel supply, avariable-ratio lever device for changing the magnitude of one of saidtwo signals, and a regulating system subject to manual supervision foradjusting the variable-ratio device.

6. In a fuel control for an engine having an air intake system with acompressor therein, a fuel control member for controlling the rate ofengine fuel supply, a servo motor for positioning said control member, acontrol element for controlling the servo motor, an actuating mechanismfor said control element, air pressure responsive means connected withsaid air intake system for trans mitting to said actuating mechanism afirst signal in the direction to increase the rate of engine fuelsupply, a feedback spring connected with said fuel control member fortransmitting to said actuating mechanism a second signal opposed to thefirst signal and indicative of the rate of engine fuel supply, avariable-ratio lever device for changing the magnitude of one of saidtwo signals, and means responsive to parameters of engine operation foradjusting the variable-ratio lever device.

7. In a fuel control for a power plant having an air induction systemleading to a combustion chamber, a compressor in said induction system,a fuel supply system for feeding fuel to the combustion chamber, a fuelcontrol member in said fuel supply system for regulating the rate offuel flow to the combusion chamber, a servo device for positioning saidfuel control member, a servo control element for controlling said servodevice, means responsive to compressor discharge pressure for producinga first control force varying in direct proportion to absolutecompressor discharge pressure, a feed-back spring connected to said fuelcontrol member for producing a second control force which various withchanges in the position of said fuel control member, power plant controlmeans subject to manual supervision for producing a variable controlsignal, multiplying means for multiplying said variable control signaland one of said control forces to provide a resultant force, a firstoperating connection for transmitting said resultant force to said servocontrol element in one direction, and a second operative connection fortransmitting the other, non-multiplied control force to the same servocontrol element in the opposite direction.

8. In a fuel control for a power plant having an air induction systemwith a compressor therein, a combustion chamber and a manually operablecontrol lever, a fuel supply system with a control member for regulatingthe rate of fuel flow to the combustion chamber, means responsive to theposition of said lever for providing a first signal, means responsive tocompressor discharge pressure for providing a second signal, meansresponsive to tempera ture in the air induction system for providing athird signal, means for receiving said signals to provide a resultantsignal, a spring responsive to the position of the control member forproviding a feedback signal, and a servo device controlled by saidresultant signal and feedback signal for positioning the control member.

9. In a fuel control for a power plant having an air induction systemwith a compressor therein and a combustion chamber, a fuel supply systemwith :a control member for regulating the rate of fuel flow to thecombustion chamber, means responsive to compressor discharge pressurefor providing a first signal, means responsive to temperature in the airinduction system for providing a second signal, means for receiving saidsignals to provide a resultant signal, means responsive to the positionof the control member for providing a feedback signal, and a servodevice controlled by said resultant signal and feedback signal forpositioning the control member.

10. In a fuel control for a power plant having an air induction systemand a combustion chamber, a fuel supply system with a control member forregulating the rate of fuel flow to the combustion chamber, meansresponsive to pressure in said air induction system for providing afirst signal, means responsive to temperature in said air inductionsystem for providing a second signal, means for receiving said signalsand providing a resultant signal, means for receiving said signals andproviding a. resultant signal, means responsive to the adjustment of thecontrol member for providing a feedback signal, and a servo devicecontrolled by said resultant signal and feedback signal for adjustingthe control member.

11. In a fuel control for a power plant having a combustion chamber, afuel supply system with a control member for regulating the rate of fuelflow to the combustion chamber, a plurality of means responsive tovarious parameters of power plant operation for providing correspondingsignals, means for receiving said signals to provide a resultant force,means responsive to the adjustment of the control member to provide afeedback force, a servo device for adjusting the control member, servocontrol means for controlling the operation of said servo device, meansfor applying said resultant force to said servo control means in onedirection, and means for applying said feedback force to the same servocontrol means in the opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,999,488September 12, 1961 Ferdinando Carlo Reggio I It is hereby certified thaterror appears in ,the above numbered patentrequiring correction and thatthe said Letters Patent should read as corrected below.

Column 3, line 53, for "and" read the column 6, lines 28 and 29, strikeout "means for receiving said signals and providing a resultantsignal,".

Signed and sealed this 6th day of February 1962 (SEAL) Attest:

ERNEST W. 'SWIDER Attesting Officer DAVID L. LADD Commissioner ofPatents

